8C Microbes and Disease

What are microbes?

Microbes are very small living things and are sometimes called micro-organisms.Microbes are so tiny that they cannot be seen with the naked eye. They can only be seen using a microscope.

How many different microbes can you name?

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Different types of microbes

There are three types of microbes:

microbes bacteria viruses fungi

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Bacteria fact file

Bacteria e.g. Salmonella and Streptococcussize: 1/1000 mm shape: Bacteria can be spherical, rod-shaped or comma-shaped. structure: Bacteria are singlecelled organisms, which do not completely have a nucleus. Some cause disease, but many are useful. reproduction: Bacteria reproduce very quickly. Two can very quickly become four, then eight and so on.

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Bacterium structure

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Viruses fact file

Viruses e.g. flu virus and HIV (the AIDS virus)size: 1/1,000,000 mm shape: Viruses have regular and geometric shapes. structure: A virus is a simple organism which does not display ALL the characteristics of living things. They are made up of a protein coating and some genetic material.

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Virus structure

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Fungi fact file

Fungi e.g. Penicillium and yeastsize: Some fungi can actually be seen with the naked eye, others are slightly bigger than bacterial cells. shape: Fungi come in many different shapes. structure: Fungi have the most complex structures of all the microbes. They feed off other living things.

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Fungi (yeast) structure

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Contents

8C Microbes and Disease

Using microbes bacteria and fungi

Microbes have many uses that are based on the fact that microbes can be grown.Bacteria grow in milk to make it go off. This type of bacterial growth is used to make milk into yoghurt. Cheese is another product that is made from milk.

Fungi can also be used to make food. The meat substitute Quorn is a protein produced using fungi.

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Using microbes yeast

Yeast is a type of fungus and carries out respiration. The respiration of this microbe can be used in different ways in baking bread and in brewing.The aerobic respiration of yeast is used to make bread rise. Yeast uses the sugar in bread dough to carry out aerobic respiration:

glucose

oxygen

carbon dioxide

water

energy

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Using microbes yeast

The anaerobic respiration of yeast is used to make beer and wine.In this case, the yeast respires without oxygen and produces alcohol (ethanol). This process is known as fermentation. Yeast converts the sugar into alcohol by anaerobic respiration:

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Which type of microbe?

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How do microbes enter the body?

eyes ears mouth nose

skin cuts genitals

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How are microbes spread?

The spreading of microbes and disease is known as transmission.1. Transmission by air A cough or a sneeze can release millions of microbes into the air which can then infect somebody else.

2. Transmission by waterDirty water can transmit many diseases, e.g. cholera, which can be transmitted by drinking.

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How are microbes spread?

3. Transmission by animalsAn animal can carry a microbe from one place to another, e.g. a mosquito which spreads the malaria parasite. 4. Transmission by contact

Many microbes can be exchanged from one person to another by direct or indirect contact: direct contact by hand; indirect contact, e.g. by walking on a wet floor already contaminated by someone else who has athletes foot; sexual contact.1 of 20 20 of 31 Boardworks Ltd 2004 2005

How are microbes spread?

4. Transmission by contactThere are other forms of indirect contact, e.g. the transmission of microbes from mother to unborn child. Transmission through the placenta If the mother develops the HIV/Aids infection, it can be passed on to the unborn child through the placenta. Transmission via breastfeeding If a child is being breastfed, he or she can also pick up microbes from the mother via the mothers milk.1 of 20 21 of 31

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How is the spread of disease stopped?

The spread of disease can be prevented by making sure that good hygiene is used in key places such as bathrooms and kitchens.

Chemicals called antibiotics can be used to treat bacterial infections.

People can be immunized against some diseases by the injection of a vaccine.

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8C Microbes and Disease

Fighting microbesHow does the body fight off microbes that cause disease?

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What do white blood cells do?

The human body has a number of natural defences against microbes. Noses are hairy inside to trap microbes!The body also produces white blood cells to help defend it from microbes. white blood cell

antibody Some white blood cells are able to produce chemicals called antibodies. These pairing with matching antigens on the surfaces of microbes and so help the white blood cells to engulf microbes.1 of 20 25 of 31 Boardworks Ltd 2004 2005